From stern@rowland.harvard.edu Fri Nov 16 08:58:23 2007 From: Alan Stern Date: Fri, 16 Nov 2007 11:58:15 -0500 (EST) Subject: USB: power-management documenation update To: Greg KH , Tilman Schmidt Cc: USB development list Message-ID: This patch (as1014) was partly written by Tilman Schmidt. It clarifies the USB power-management documentation by explaining that when a disconnect occurs, a suspend method call might not be followed by either a resume or a reset_resume call. Signed-off-by: Alan Stern Signed-off-by: Tilman Schmidt Signed-off-by: Greg Kroah-Hartman --- Documentation/usb/power-management.txt | 8 ++++++++ 1 file changed, 8 insertions(+) --- a/Documentation/usb/power-management.txt +++ b/Documentation/usb/power-management.txt @@ -278,6 +278,14 @@ optional. The methods' jobs are quite s (although the interfaces will be in the same altsettings as before the suspend). +If the device is disconnected or powered down while it is suspended, +the disconnect method will be called instead of the resume or +reset_resume method. This is also quite likely to happen when +waking up from hibernation, as many systems do not maintain suspend +current to the USB host controllers during hibernation. (It's +possible to work around the hibernation-forces-disconnect problem by +using the USB Persist facility.) + The reset_resume method is used by the USB Persist facility (see Documentation/usb/persist.txt) and it can also be used under certain circumstances when CONFIG_USB_PERSIST is not enabled. Currently, if a